Mortality surveillance of a US wide cohort of chemical industry workers.

Objective: To evaluate the mortality for an occupational cohort and discuss its suitability as an internal comparison population.

Methods: The study included 114,683 employees who worked at 1 of 25 US locations between January 1, 1960, and December 31, 2005. Standardized mortality ratios (SMRs) and 95% confidence intervals (CIs) were calculated based on US rates.